It has been recognised that a balanced diet must include an adequate level of dietary fibre. There are many natural food sources of dietary fibre of which cereals, particularly bran, are recognized as a good source.
However, it would seem that a high proportion of diets of people of the developed countries contain an inadequate level of dietary fibre. An inadequate level of dietary fibre has been linked with a number of diseases which may be broadly classified as metabolic and gastrointestinal. Examples of these diseases are diabetes mellitus, diverticular disease and colonic cancer.
It has also be found that some forms of dietary fibre are useful in lowering blood cholesterol.
One approach to providing adequate levels of dietary fibre has been to produce processed foods which are high in dietary fibre content. Such foods include breakfast cereals, snack bars, bread and the like. Typically bran, outer tissues of the kernel, including pericarp from a variety of cereal sources including wheat, maize, oats and other plant extracts have been used as the source of fibre.
More recently, resistant starches have been recognized as a potential source of dietary fibre. Resistant starches are starches that are highly resistant to hydration and which when ingested pass through the upper regions of the gastrointestinal tract largely unchanged.
To date the only natural sources of resistant starch at a significant level are green bananas and raw potatoes. Such sources do, however, present substantial problems in formulating satisfactory food products, in particular low gelatinization temperatures which are typically 60-80.degree. C.
It is also possible to produce resistant starch by extensive processing involving repeated cooking and cooling of starch pastes.
In copending International patent application No. PCT/AU93/00389 filed Jul. 30, 1993 entitled "High Amylose Starch and Resistant Starch Fractions" there is disclosed a hybrid maize seed which is capable of producing a starch having an amylose content of more than about 80%. That application further discloses a maize starch derived from such seed having a amylose content of more than about 80%. This starch was designated as "High Amylose Starch" in view of the surprising high amylose content. A number of examples of compositions including high amylose starch were given which included a number of food applications.
Surprisingly, it has now been found that the aforementioned high amylose starch is high in dietary fibre content and is a resistant starch. Moreover, it has been found that such starches may be advantageously incorporated into food products to achieve enhanced levels of dietary fibre content. Additionally, these starches have relatively high gelatinization temperatures, typically 160-170.degree. C.